;;; Exercise 1.4.  Observe that our model of evaluation
;;; allows for combinations whose operators are compound expressions.
;;; Use this observation to describe the behavior of the following procedure:

(define (a-plus-abs-b a b)
  ((if (> b 0) + -) a b))

; if cond true false
; se b > 0 => + => (+ a b)
; se b < 0 => - => (- a b) => (- 2 -3)
; no formato algébrico
; 2 - (-3) => 2 + 3


